Venezuela's military said Sunday it repelled a paramilitary "terrorist" attack on one of its bases in the city of Valencia led by a deserted army officer allegedly linked to "foreign governments."
Military helicopters could be seen flying over the major northern city as tactical armored vehicles patrolled the streets in a climate of tension.
Strong explosions were heard by a team of AFP journalists.
Locals said a nighttime curfew had been imposed, as flaming barricades set up in the street by anti-government protesters spewed black smoke.
Officials insisted that several of the "terrorists" had been arrested and that all was normal across the country.
Still, the incident heightened fears that Venezuela's deepening political and economic crisis could yet explode into extreme violence.
The armed forces said in a statement "a group of civilian criminals wearing military uniforms and a first lieutenant who had deserted" carried out the attack, during which a number of weapons were stolen. Local journalists reported hearing firing at the base.
The lieutenant and several of the attackers were arrested but "an intense search" was on for the others who made off with the guns, the military said.
The statement said those detained had "confessed" to being hired by "extreme-right activists, in connection with foreign governments." It did not identify those governments.
Venezuela has become increasingly isolated internationally as President Nicolas Maduro has tightened his hold on power through a contested new loyalist assembly that started work this week, bolstered by the staunch backing of the military.
The opposition, which controls the legislature, has become sidelined. Its leaders are under threat of arrest after organizing protests, fiercely countered by security forces, that have left 125 people dead in the past four months.
The new Constituent Assembly, packed with Maduro allies including the president's wife and son, has quickly used its supreme powers to clamp down on dissent.
On Saturday, it ordered the dismissal of the attorney general, Luisa Ortega, who had broken ranks with Maduro to become one of his most vociferous critics.
And on Sunday it announced the creation of a "truth commission" Maduro said he wanted to probe alleged crimes by the opposition.
The United States accuses Maduro of installing an "authoritarian dictatorship" that has turned Venezuela into an international pariah.
The US, Colombia, Chile, Guatemala, Mexico, Panama and Peru have slammed the "illegal" sacking of Ortega.
And Argentina, Uruguay, Paraguay and Brazil have indefinitely suspended Venezuela from the South American trading bloc Mercosur for its "rupture of the democratic order."
"Each step by the Constituent Assembly is a step towards the precipice by this government," the leader of the opposition parliament, Julio Borges, told a news conference in Caracas on Sunday.
"The only thing there is, is brute force. This is not a strong government, it's a lost government, which is falling. The only thing it wants to do is cling to power," he said, calling for more protests.
Borges said the Venezuelan military "is a mirror of a country that wants change."
The opposition has repeatedly urged the military to abandon Maduro.
But Defense Minister Vladimir Padrino, who is also head of the armed forces, has said the military's loyalty was unshakable.
After Sunday's attack in Valencia, Padrino tweeted that the assailants "couldn't do anything against" the army. "They try to assault it with terrorist attacks. They can't," he said.
In a video posted online just before the attack, a man presenting himself as an army captain declared a "legitimate rebellion... to reject the murderous tyranny of Nicolas Maduro."
Speaking with 15 other men dressed in camouflage standing by him, some of them armed, he demanded a transitional government and "free elections."
It was not known if he was the deserted lieutenant referred to in the military statement.
That statement said the officer had absconded three years ago and taken refuge in Miami, in the US state of Florida.
The deputy leader of Maduro's Socialist Party, Diosdado Cabello, tweeted that there was "absolute normality in the other military units in the country."